In view of the increase cost of energy, a major consideration in the operating cost of a pyro-processing system is its energy economy. It is also of importance that gas be cleaned prior to venting to stack and not in itself be a source of pollution.
A general object of the present invention is to recycle preheat off-gas and utilize the heat therein for the system.
Still another object of the present invention is to boost the temperature of the preheat gas and utilize this gas in the grate.
Yet another object of the present invention is to bypass a higher concentration of dirty gas from the kiln by reducing the gas flow through the kiln.
A further object of the present invention is to provide a means whereby it is possible to balance kiln conditions to improve kiln system operating conditions and minimize waste gas temperature.
A still further object of the present invention is to provide for two recycle potentials: (1) preheat gas recycle; and, (2) up-draft drying gas recycle.
A further object of the present invention is to effect an operating cost reduction by burning unburned kerogen volatiles, utilizing the heat therefrom as system heat.
Still another object of the present invention is to remove dust from the gas before it is utilized in the system to protect the equipment.
Another object of the present invention is to reduce SO.sub.2 emissions which are passed to the atmosphere from about 2000 p.p.m. to at least 200 p.p.m., thereby reducing system fouling and also meeting environmental standards.